System and method for point of use delivery, control and mixing chemical and slurry for CMP/cleaning system

ABSTRACT

A chemical mechanical planarization system includes a point of use chemical mixing system. The point of use chemical mixing system includes a first and a second pump, a first and a second flow sensor, a mixer and a controller. The first pump has an input coupled to a first chemical supply and the first flow sensor coupled to the output of the first pump. The second pump has an input coupled to a second chemical supply and the second flow sensor coupled to the output of the second pump. The mixer has inputs coupled to the output of the first and second flow sensors. The controller is configured to receive signals from the first and second flow sensors and to produce control signals for the first and second pumps and the mixer. The controller is further configured to cause a mixture of the first and second chemicals upon a demand from the CMP process.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to semiconductor waferplanarizing, and more particularly, to methods and systems forcontrolling and mixing chemicals for a chemical mechanical planarizingprocess.

[0003] 2. Description of the Related Art

[0004] In the fabrication of semiconductor devices, there is a need toperform a variety of substrate preparation and fabrication operationsincluding chemical mechanical planarization (CMP) operations, substratecleaning, substrate polishing and buffing, substrate rinsing and drying,and other similar operations. Planarization, polishing, and cleaningoperations are routinely performed on semiconductor wafers at variousstages in the fabrication process. Typically, such operations areefficiently combined within process systems that are configured, forexample, to receive batches of wafers at a time to be processed throughCMP, polishing, buffing, cleaning, rinsing, and/or drying, followed bywafer processing through subsequent wafer fabrication operations.

[0005] Typically the chemicals required for such a CMP processes areprepared in a batch process system 100 such as shown in FIG. 1. FIG. 1is a schematic diagram of a prior art system for mixing chemicals for aCMP process. A first chemical 101 is stored in a first supply tank 102and a second chemical 103 is stored in a second supply tank 104. When abatch of the first and second chemicals 101, 103, is mixed, therespective supply valves 106, 108 are opened and a selected amount ofthe first and second chemicals 101, 103 are transferred to the batchmixing tank 110. The first and second chemicals 101, 103 are then mixedin the batch-mixing tank 110. Typically the mixed batch is testedthrough manual processes such as weighing the respective quantities ofthe first and second chemicals 101, 103 that are added to the batchmixing tank 110. Once the mixed batch of the chemicals is fully preparedand ready to be used, the batch supply valve 120 is opened and thebatch-mixing tank 110 is pressurized to cause the mixture 123 to flow toa delivery tank 122. The delivery tank 122 can then be pressurized todeliver the mixture 123 to a mixture distribution manifold 124. Themanifold 124 distributes the mixture to multiple points of use 130, 132,134, through point of use supply valves 136, 138, 140 respectively. Eachof the points of use 130, 132, 134 can represent a different CMP processtool or different locations within a single CMP process tool.

[0006] One of the problems with the batch process system 100 describedabove is that often the mixture 123 can only be used for a limited timeperiod. For example, often, optimum CMP results require the mixture beused within the first sixty minutes after the mixture 123 is formed inthe batch-mixing tank 110. The time limits may be due to reactivity ofthe mixture 123 or due to coagulation effects common to the slurry-typechemical used in the CMP process.

[0007] Another problem with the batch process system 100 is that themixture 123 must be transferred to each point of use 130, 132, 134 via adistribution system (e.g., the manifold 124, the respective point of usesupply valves 136, 138, 140 and interconnecting piping). When each batchof the mixture 123 expires or is no longer needed, the entiredistribution system must be fully flushed and cleaned so that impuritiesof the previously expired batch do not contaminate successive batchmixtures. Further, the remaining mixture 123 contained in thedistribution system becomes a waste product that must be disposed ofwhich is both inefficient and typically expensive.

[0008] Yet another problem with the batch process system 100 is thatoften the mixture 123 is hazardous (e.g., caustic, acidic, flammable,poisonous, etc.). Because the mixture 123 is hazardous, the pressurizedbatch mixing tank 100 and delivery tank 122 must be very closelymonitored and controlled. Further the batch-mixing tank 100 and deliverytank 122 are typically double walled to provide added safety containmentof the hazardous mixture 123. The safety requirements of storing andpressurizing quantities of the hazardous mixture 123 increase thecomplexities of the batch process system 100 and the cost. Therefore thebatch process system 100 is more expensive and less reliable thanrequired.

[0009] Typically the batch process system 100 yields inconsistentbatches because one batch is not exactly the same as another batch.Inconsistent batches often cause inconsistent CMP process results. Thebatches may be inconsistent because the measurements, such as therespective amounts of the first and second chemicals 101, 103, aredifferent from one batch to another or because one batch has aged longerbefore use than another batch.

[0010] Similarly, the batch process system 100 does not produce acontinuous and consistent mixture. This is because typical mixturecontrol is in the batch mixing process in the batch-mixing tank 110.Once the mixture 123 is combined in the batch mixing tank 100 theretypically is no further monitoring or testing to determine if themixture is correct or becomes too aged or contaminated. As a result, ifthe mixture 123 becomes incorrect, then the CMP results could alsobecome incorrect.

[0011] Another problem with most batch-type mixing systems is that aquantity of the mixture 123 is prepared in advance of the actual need ofthe mixture 123. If for any reason the mixture 123 is not needed (e.g.,the CMP process is delayed until after the mixture 123 is too aged),then the entire mixture 123 must be discarded as a waste product. Thisresults in excessive waste, which is both inefficient and typicallyexpensive.

[0012] In view of the foregoing, there is a need for a more efficient,accurate delivery system of the CMP chemicals.

SUMMARY OF THE INVENTION

[0013] Broadly speaking, the present invention fills these needs byproviding a point of use chemical mixing system in a chemical mechanicalplanarization system. It should be appreciated that the presentinvention can be implemented in numerous ways, including as a process,an apparatus, a system, computer readable media, or a device. Severalinventive embodiments of the present invention are described below.

[0014] A chemical mechanical planarization system includes a point ofuse chemical mixing system. The point of use chemical mixing systemincludes a first and a second pump, a first and a second flow sensor, amixer and a controller. The first pump has an input coupled to a firstchemical supply and the first flow sensor coupled to the output of thefirst pump. The second pump has an input coupled to a second chemicalsupply and the second flow sensor coupled to the output of the secondpump. The mixer has inputs coupled to the output of the first and secondflow sensors. The controller is configured to receive signals from thefirst and second flow sensors and to produce control signals for thefirst and second pumps and the mixer. The controller is furtherconfigured to cause a mixture of the first and second chemicals upon ademand from the CMP process.

[0015] A method of mixing two or more chemicals for a CMP systemincludes pumping a first and a second chemical to a point of use.Monitoring a flow rate of the first chemical from a first pump andmonitoring a flow rate of the second chemical from a second pump.Controlling the flow of the first and second chemicals into a mixer upondemand for a mixture of the first and second chemicals. Outputting themixture to the CMP process.

[0016] In one embodiment, the flow of the first and the second chemicalsinto the mixer is controlled according to an aspect of the mixture suchas a pH level of the mixture or a density of the mixture.

[0017] In one embodiment, the first and second pumps include atubephram-type pump.

[0018] Mixing the CMP chemicals, upon demand, at the point of usereduces waste and provides more accurate and consistent chemicalmixtures. A point of use mixing system also allows constant feedback andcontrol of the mixing process. Point of use mixing also reduces cost andcomplexity over prior-art batch mixing systems.

[0019] Point of use mixing also reduces waste by substantiallyeliminating mixtures produced before being required and by reducing thesize of the distribution system for the mixtures.

[0020] Other aspects and advantages of the invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, illustrating by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings, andlike reference numerals designate like structural elements.

[0022]FIG. 1 is a schematic diagram of a prior art system for mixingchemicals for a CMP process.

[0023]FIG. 2A is a piping and instrumentation diagram (P&ID) of a pointof use mixing system using two chemicals in accordance with oneembodiment of the present invention.

[0024]FIG. 2B is a flowchart diagram that illustrates the methodoperations performed in controlling the flow of the first chemical in apoint of use mixing system 200 in accordance with one embodiment of thepresent invention.

[0025]FIG. 2C is a flowchart diagram that illustrates the methodoperations performed in controlling the flow of the first chemical in apoint of use mixing system in accordance with one embodiment of thepresent invention.

[0026]FIG. 2D is a flowchart diagram that illustrates the methodoperations performed in controlling the flow of the second chemical in apoint of use mixing system in accordance with one embodiment of thepresent invention.

[0027]FIG. 2E is a block diagram of the proportional, integral,derivative (PID) controls in controlling the flow of the first chemical101 in a point of use mixing system in accordance with one embodiment ofthe present invention.

[0028]FIG. 3 is a piping and instrumentation diagram (P&ID) of a mixerusing two chemicals in accordance with one embodiment of the presentinvention.

[0029]FIG. 4A illustrates a rotary pump 400 in accordance with oneembodiment of the present invention.

[0030]FIGS. 4B and 4C show cross-sections of the compressible tubing atthe A section shown in FIG. 4A.

[0031]FIG. 4D shows a cross-section of the compressible tubing at the Bsection shown in FIG. 4A.

[0032]FIG. 4E shows particles that can be aggregated when the particlesare compressed between the sidewalls of the tubing.

[0033]FIG. 5 illustrates a tubephram type pump in accordance with oneembodiment of the present invention.

[0034]FIG. 6 is a piping and instrumentation diagram (P&ID) of a pointof use mixing system using three chemicals and a flushing system inaccordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0035] Several exemplary embodiments for a chemical mechanicalplanarization system including a point of use chemical mixing systemwill now be described. It will be apparent to those skilled in the artthat the present invention may be practiced without some or all of thespecific details set forth herein.

[0036] Point of use mixing CMP chemicals can result in more efficientuse of the chemicals and reduce the waste products such as excessmixture in a mixture distribution system or excess batch-preparedmixture. In addition a point-of use mixture system can provide acontinuous flow of the mixture. If the mixture is also continuouslymonitored, a feedback control loop can also be established to maintain amore constant mixture.

[0037]FIG. 2A is a piping and instrumentation diagram (P&ID) of a pointof use mixing system 200 using two chemicals in accordance with oneembodiment of the present invention. Although FIG. 2A illustrates a twochemical point of use system, the system and processes described belowcan also be extended to three or more chemicals. A first chemical 101such as a first slurry (e.g., Hitachi slurry PN HFA005 or other suitableslurry) is stored in a first supply tank 102. A second chemical 103 suchas deionized water (DI water) or a second slurry or other chemical to bemixed with the first chemical, is stored in a second supply tank 104. Apoint of use mixer 210 includes a several components that mix the firstand second chemicals 101, 103. Specifically, the point of use mixerincludes a first supply valve 212 is disposed between the first supplytank 102 and an input of a first pump 214. An output of the first pump214 is coupled to an input of a first flow sensor 216. An output of thefirst flow sensor 216 is coupled to a first input to a mixer 220. Asecond supply valve 232 is disposed between the second supply tank 104and an input of a second pump 234. An output of the second pump 234 iscoupled to an input of a second flow sensor 236. An output of the secondflow sensor 236 is coupled to a second input to the mixer 220. An outputof the mixer 220 is coupled to the CMP process tool 250. A controller240 is electrically coupled to the first and second supply valves, 212,232, the first and second pumps 214, 234, the first and second flowsensors 216, 236 and the mixer 220.

[0038] The first and second pumps 214, 234 can also include a first andsecond pressure regulators 217, 237, respectively. The pressureregulators 217, 237 reduce or dampen the normal pressure fluctuationscaused by the first and second pumps 214, 234. The output of the mixer220 can also include a monitor sensor that can be electrically coupledto the controller 240. The first and second supply valves 212, 232 canbe normally closed valves so that without a control input the first andsecond supply valves 212, 232 are automatically closed. Normally closedvalves increase the safety of the control of the first and secondchemicals 101, 103, respectively.

[0039] In operation, the controller 240 opens the first supply valve 212and activates the first pump 214 so that the first pump 214 can draw thefirst chemical toward the mixer 220. The first flow sensor 216 thendetects the flow rate of the first chemical 101 toward the mixer 200 andoutputs the detected flow rate to the controller 240. The controllerthen uses the detected flow rate obtained from first flow sensor 216 toadjust the flow rate of the first chemical to the desired flow rate.

[0040] Simultaneously with the first chemical 101 flowing into the mixer220, the second chemical 103 is also pumped into the mixer at acontrolled, desired flow rate through the second supply valve 232, thesecond pump 234 and the second flow sensor 236, respectively. Thedesired flow rate of the first chemical 101 and the desired flow rate ofthe second chemical 103 are combined in the mixer 220 to produce adesired mixture in the mixer 220.

[0041] The controller 240 forms a closed loop control system of the flowrate of the first chemical 101 by measuring the flow rate through thefirst flow sensor 216 and adjusting the pumping speed of the pump 214 tomaintain the desired flow rate of the first chemical 101. Similarly, thecontroller 240 forms a closed loop control system of the flow rate ofthe second chemical 103 by measuring the flow rate through the secondflow sensor 236. The controller 240 then adjusts the pumping speed ofthe second pump 234 to maintain the desired flow rate of the secondchemical 103. By maintaining a known flow rate of the first and secondchemicals 101, 103 into the mixer 220, the mixture of the desiredproportions of the first and second chemicals 101, 103 can becontinuously maintained.

[0042]FIG. 2B is a flowchart diagram that illustrates the methodoperations 252 performed in controlling the flow of the first chemicalin a point of use mixing system 200 in accordance with one embodiment ofthe present invention. In operation 253, the first chemical 101 ispumped to the point of use mixing system. The flow rate of the firstchemical 101 is monitored in operation 254. In operation 255, the secondchemical 103 is pumped to the point of use mixing system. The flow rateof the second chemical 103 is monitored in operation 256. In operation257 the flow of the first and second chemicals to the mixer arecontrolled according to demand for the mixture of the first and secondchemicals 101, 103. In operation 258, the mixture is output to be usedsuch as in a CMP process.

[0043]FIG. 2C is a flowchart diagram that illustrates the methodoperations performed in controlling the flow of the first chemical in apoint of use mixing system 200 in accordance with one embodiment of thepresent invention. FIG. 2D is a flowchart diagram that illustrates themethod operations performed in controlling the flow of the secondchemical in a point of use mixing system 200 in accordance with oneembodiment of the present invention. To simplify discussion, the controlof the flow of the first and second chemicals 101, 103 will be describedseparately. However, in at least one embodiment, the controller 240simultaneously controls the flow rates of the first and second chemicals101, 103.

[0044] In FIG. 2C, in operation 262, the controller 240 causes the firstsupply valve 212 to open and the first pump 214 to draw the firstchemical 101 into the mixer 220. In operation 264, the first flow sensor216 detects the flow rate of the first chemical 101 output from thefirst pump 214. The flow sensor 216 communicates the detected flow rateto the controller 240. In operation 266, the detected flow rate of thefirst chemical 101 is compared to the desired flow rate of the firstchemical 101. If, in operation 266, the detected flow rate of the firstchemical 101 is equal to the desired flow rate of the first chemical,then, in operation 268 the desired flow rate is examined. If inoperation 268, the desired flow rate is equal to zero “0” then themethod operations end. If, in operation 268, the desired flow rate isnot equal to zero “0” then the method operations continue in operation264.

[0045] If, in operation 266, the detected flow rate of the firstchemical 101 is not equal to the desired flow rate of the firstchemical, then, in operation 270 the detected flow rate is examined todetermine if the detected flow rate is greater than the desired flowrate. If, in operation 270, the detected flow rate is greater than thedesired flow rate then in operation 272 the controller 240 reduces theflow rate from the first pump 214. The method operations then continuein operation 264 as described above. If in operation 270, the detectedflow rate is not greater than the desired flow rate then in operation274 the controller 240 increases the flow rate from the first pump 214.The method operations then continue in operation 264 as described above.

[0046] In FIG. 2D, in operation 282, the controller 240 causes thesecond supply valve 232 to open and the second pump 234 to draw thesecond chemical 103 into the mixer 220. In operation 284, the secondflow sensor 236 detects the flow rate of the second chemical 103 outputfrom the second pump 234. The flow sensor 236 communicates the detectedflow rate to the controller 240. In operation 286, the detected flowrate of the second chemical 103 is compared to the desired flow rate ofthe second chemical 103. If, in operation 286, the detected flow rate ofthe second chemical 103 is equal to the desired flow rate of the secondchemical, then, in operation 288 the desired flow rate is examined. If,in operation 288, the desired flow rate is equal to zero “0” then themethod operations end. If, in operation 288, the desired flow rate isnot equal to zero “0” then the method operations continue in operation284.

[0047] If, in operation 286, the detected flow rate of the secondchemical 103 is not equal to the desired flow rate of the secondchemical, then, in operation 290 the detected flow rate is examined todetermine if the detected flow rate is greater than the desired flowrate. If, in operation 290, the detected flow rate is greater than thedesired flow rate then in operation 292 the controller 240 reduces theflow rate from the second pump 234. The method operations then continuein operation 284 as described above. If in operation 290, the detectedflow rate is not greater than the desired flow rate then in operation294 the controller 240 increases the flow rate from the second pump 234.The method operations then continue in operation 284 as described above.

[0048] Alternatively, the controller 240 can create a closed-loopfeedback control by monitoring one or more aspects of the mixture outputfrom the mixer 220. A mixture sensor 242 monitors the mixture. In oneembodiment, the mixture sensor 242 includes a pH sensor. The pH sensorcan continuously measure the pH level of the mixture. For example, in apoint of use mixing system a pH level of 8.02 represents the pH level ofthe desired mixture. Further, the first chemical 101 has a higher pHlevel than the second chemical 103. If the controller detects a mixturepH level of 8.01, then the controller can automatically adjust theproportion of the first and second chemicals 101, 103 to increase thedetected pH level to the desired 8.02 level.

[0049]FIG. 2E is a block diagram 350 of the proportional, integral,derivative (PID) controls in controlling the flow of the first chemical101 in a point of use mixing system 200 in accordance with oneembodiment of the present invention. Although the PID controls aredescribed in relation to controlling the flow of only the first chemical101 the same principles are applicable to controlling any other controlvariable such as controlling the flow of the second chemical 103 orcontrolling other aspects of the mixture 123. A desired setpoint, suchas a desired flow rate of the first chemical 101, is applied to theinput 352. The proportional, integral, derivative variables K_(p),K_(i), K_(d) are extracted from the signal applied to the input 352.Each of the PID variables are applied to corresponding PID calculations354A, 354B, 354C to produce a control signal 356 at the output 358. Forexample the control signal output may be a first pump 214 speed controlsignal. The control signal 356 is then applied to the process (e.g.,first pump speed control signal applied to the control input of thefirst pump 214, etc.). A feedback signal 360 is fed back to the input352 to provide an error control/feedback. If the setpoint applied to theinput 352 is the desired flow rate of the first chemical 103, then thefeedback signal 360 may be a detected flow rate of the first chemical103 from the first pump 214 such as from the first flow sensor 216.

[0050]FIG. 3 is a piping and instrumentation diagram (P&ID) of a mixer220 using two chemicals in accordance with one embodiment of the presentinvention. Although FIG. 3 illustrates a two chemical mixer, the systemand processes described below can also be extended to three or morechemicals. A first mixer input valve 222 controls input of the firstchemical 101 from the first flow sensor 216 to the mixer manifold 226. Asecond mixer input valve 224 controls input of the second chemical 103from the second flow sensor 236 to the mixer manifold 226. The first andthe second chemicals 101, 103 mix in the mixer manifold 226. A mixeroutput valve 228 controls the output from the mixer manifold 226 to theCMP process 250.

[0051] In one embodiment, the piping dimensions (e.g., lengths anddiameters of the interconnecting piping) between each the input valves222, 224 and the mixing manifold 226 are the same. In one embodiment themixer 220 is a radial valve mixer such that each input valve 222, 224are located on opposing sides and equidistant from a center mixingmanifold. An example of a suitable radial valve miser is a series 089M &079NC manifold assembly available from Bio-Chem Valve, Inc. of 85 FultonStreet, Boonton, N.J. Alternatively, the mixer 220 can be a linearconfiguration similar to the mixer 220 illustrated in FIG. 3.

[0052]FIG. 4A illustrates a rotary pump 400 in accordance with oneembodiment of the present invention. The first and second pumps 214, 234can be a rotary pump such as shown in FIG. 4A. A rotary pump 400includes a housing forming an approximately round inner chamber 404. Arotor 406 is centered in the inner chamber 404. The rotor includes twoor more (in this instance three) compressor wheels 408A, 408B, 408C. Thehousing 402 also includes an inlet 410 and an outlet 412 that aresubstantially tangential to the inner chamber 404. Compressible tubing420 is routed through the inlet 410 around the inner circumference ofthe chamber 404 and out the outlet 412. The compressor wheels 408A,408B, 408C compress the compressible tubing 420 against the innercircumference of the chamber 404. In operation, as the rotor 406 isrotated in a counter-clockwise direction about the center axis 414 acompressor wheel presses the compressible tubing 420 against the innercircumference of the chamber 404. A volume, such as the volume 422, istrapped between compressor wheels 408B, 408C. The volume 422 includes afluid such as the first chemical 101. As the rotor 406 continues torotate counter-clockwise, the volume 422 of the first chemical 101 ispropelled toward and eventually out the outlet 412. A nearly continuousflow of the first chemical 101 can thereby be nearly continuous.

[0053]FIG. 4B shows a cross-section of the compressible tubing 420 atthe A section as shown in FIG. 4A. Initially the cross-section of thecompressible tubing 420 is substantially round. As the tubing issuccessively compressed over an extended time, the sidewalls of thecompressible tubing 420 begin to deform and the cross-section begins toresemble an oval as shown in FIG. 4C. The area of the oval cross-sectionshown in FIG. 4C is substantially less than the area of the circularcross-section of FIG. 4B. When the tubing becomes deformed into an ovalcross-section the volume (such as volume 422 above) between twocompressor wheels is reduced and therefore the volume pumped perrotation is reduced.

[0054]FIG. 4D shows a cross-section of the compressible tubing 420 atthe B section shown in FIG. 4A. When the compressor wheel 408Bcompresses the tubing 420 against the inner wall of the chamber 404, thesidewalls of the tubing 420 are pressed together. As a result, particlescan be dislodged from the walls of the tubing 420. The dislodgedparticles are then released into the chemical (e.g., the first chemical101) being pumped.

[0055]FIG. 4E shows particles that can be aggregated when the particlesare compressed between the sidewalls of the tubing 420. Originalparticles 450 are typical particles such as abrasive particles that maybe included in a CMP slurry that is being pumped. The original particleshave a tendency to aggregate together to form aggregated particles 460.When aggregated particles 460 are compressed together, such as when theparticles are compressed between the sidewalls of the tubing 420, theparticles can be chained together to form even larger chained particles470.

[0056]FIG. 5 illustrates a tubephram type pump 500 in accordance withone embodiment of the present invention. The tubephram type pump 500includes a centrally located axis 502. A cam 504 rotates on the axis502. A left slide shaft 506 and a right slide shaft 508 ride against thesurface of the cam 504. As the cam rotates, the right and left sideshafts 506, 508 slide right and left respectively to compress a righttubephram 510 and a left tubephram (not shown) respectively. The righttubephram 510 is coupled to the inlet 512 and the outlet 514. A rightinlet check valve 516 allows fluid to flow from the inlet 512 into theright tubephram 510. When the right slide shaft 508 is pressed right tocompress the right tubephram 510, the fluid pressure inside the righttubephram 510 increased. As the pressure inside the right tubephram 510increases the right inlet check valve 516 closes and a right outletcheck valve 518 opens and the pressurized fluid flows out the outlet514. As the right slide shaft 508 slides left, the right tubephram 510automatically re-forms into the shape before being compressed by theright slide shaft 508. As the right tubephram 510 re-forms, the pressureinside the right tubephram 510 decreases. When the pressure inside theright tubephram 510 decreases, the right outlet check valve 518 closesand the right inlet check valve 516 opens to draw fluid into the righttubephram 510. The left tubephram (not shown) operates similarly to theright tubephram 510.

[0057] A tubephram type pump is available from Iwaki Walchem of 5Boynton Road Holliston, Mass. 01746, Part no. CSP-05ED-BP-S01 or similartubephram-type pumps. A tubephram type pump is preferable over a rotarypump because the tubephram pump does not fully compress the sides of thetubephram 510 together. Because the sides of the tubephram 510 are notpressed together, the particles are not pressed into chained particlessuch as shown in FIG. 4E above. Also, because the sides of the tubephram510 are not pressed together the sides of the tubephram 510 do notbreakdown as quickly and thereby produce particles into the fluidpassing through the tubephram 510. Also because the sides of thetubephram 510 are not pressed together, the sides of the tubephram 510do not deform into an oval cross-section as rapidly as the compressibletubing 420 in the rotary pump 400 described above. Therefore, theefficiency of the tubephram type pump does not suffer as quickly as therotary pump 400. In one embodiment the first and second pumps 214, 234have a flow rate range of between 15 and 250 ml/minute.

[0058] The controller 240 of FIG. 2A is any suitable type of controlleras are well known in the art. The controller 240 is configurable toreceive the inputs described above, execute the PID control signals, andproduce the outputs to control the various controllable devices (e.g.,pumps 214, 234, valves 212, 232, etc.). In one embodiment, thecontroller 240 can be a programmable logic controller (PLC) such as isavailable from Siemens or any other supplier of suitable PLCs.Alternatively, the controller 240 can be any type of generic computingsystem such as a personal computer.

[0059]FIG. 6 is a piping and instrumentation diagram (P&ID) of a pointof use mixing system 600 using three chemicals and a flushing system inaccordance with one embodiment of the present invention. Although FIG. 6illustrates a three chemical point of use system, the system andprocesses described below can also be extended to four or morechemicals. A first chemical 101 is stored in a first supply tank 102. Asecond chemical 103 is stored in a second supply tank 104. A thirdchemical 602 is stored in a third supply tank 604. A point mixer 610includes a several components that mix the first, second and thirdchemicals 101, 103, 602. The point of use mixer 610 includes two supplyvalves for each of the three chemicals. Dual supply valves 606A, 606Bfor the first chemical 101. Dual supply valves 608A, 608B for the secondchemical 103. Dual supply valves 610A, 610B for the third chemical 602.Dual supply valves increase the safety of the control of the first,second and third chemicals 101, 103, 602, respectively because a failureof any one valve of a dual supply valve pairs will not allow therespective chemical to flow.

[0060] First, second and third pumps 612, 622, 632 pump the respectivefirst, second and third chemicals 101, 103, 602. First, second and thirdflow sensors 614, 624, 634 detect the flow of the first, second andthird chemicals 101, 103, 602 output from the respective first, secondand third pumps 612, 622, 632. The flow of the first, second and thirdchemicals 101, 103, 602 output from the first, second and third flowsensors 614, 624, 634 are input into three respective inputs in a fourchemical mixer 630. The first, second and third chemicals 101, 103, 602can be mixed in the four chemical mixer 630. The point of use mixingsystem 600 also includes a mixture sensor 640 to monitor the mixtureoutput from the mixer 630.

[0061] The point of use mixing system 600 further includes a deionized(DI) water system. The DI water system includes a DI water supply 650and four DI water supply valves 652, 654, 656, 658. DI water is used toflush out different portions of the point of use mixing system 600. Forexample, if the first chemical must be flushed out of the point of usemixing system 600, the dual supply valves 606A, 606B are closed. Next,the DI supply valve 652 is opened so that the DI water can flow throughthe first pump 612, the first flow sensor 614 and through the mixer 630and out the outlet of the mixer 630.

[0062] With the above embodiments in mind, it should be understood thatthe invention may employ various computer-implemented operationsinvolving data stored in computer systems. These operations are thoserequiring physical manipulation of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. Further, the manipulationsperformed are often referred to in terms, such as producing,identifying, determining, or comparing.

[0063] It will be further appreciated that the instructions representedby the operations in FIGS. 2B-2D are not required to be performed in theorder illustrated, and that all the processing represented by theoperations may not be necessary to practice the invention. Further, theprocesses described in FIGS. 2B-2E can also be implemented in softwarestored in the memory systems of the controller 240.

[0064] Although the foregoing invention has been described in somedetail for purposes of clarity of understanding, it will be apparentthat certain changes and modifications may be practiced within the scopeof the appended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims.

What is claimed is:
 1. A method of mixing two or more chemicals for aCMP system comprising: pumping a first chemical to a point of use;monitoring a flow rate of the first chemical from a first pump; pumpinga second chemical to the point of use; monitoring a flow rate of thesecond chemical from a second pump; controlling the flow of the firstand second chemicals into a mixer upon demand for a mixture of the firstand second chemicals; and outputting the mixture to a CMP process. 2.The method of claim 1, wherein controlling the flow of the first and thesecond chemicals into the mixer includes: controlling the flow rate ofthe mixer according to an aspect of the mixture.
 3. The method of claim2, wherein the aspect of the mixture includes a pH level of the mixture.4. The method of claim 1, wherein controlling the flow of the first andthe second chemicals into the mixer includes: controlling a flow rate ofthe mixture from the mixer according to the flow rate of the firstchemical.
 5. The method of claim 1, wherein controlling the flow of thefirst and the second chemicals into the mixer includes: controlling aflow rate of the mixture from the mixer according to the flow rate ofthe second chemical.
 6. The method of claim 1, wherein controlling theflow of the first and the second chemicals into the mixer includes:controlling a flow rate of the mixture from the mixer according to afirst quantity setpoint of the first chemical.
 7. The method of claim 1,wherein controlling the flow of the first and the second chemicals intothe mixer includes: controlling a flow rate of the mixture from themixer according to a second quantity setpoint of the second chemical. 8.The method of claim 1, wherein in pumping the first chemical includes:regulating the pressure to substantially reduce any pressurefluctuations.
 9. A CMP system comprising: a first pump having an inputcoupled to a first chemical supply; a first flow sensor coupled to anoutput of the first pump; a second pump having an input coupled to asecond chemical supply; a second flow sensor coupled to an output of thesecond pump; a mixer having inputs coupled to the output of the firstflow sensor and the output of the second flow sensor; and a controllerconfigured to receive signals from the first and second flow sensors andto produce control signals for the first and second pumps and the mixerand configured to cause a mixture of the first and second chemicals upona demand from a CMP process.
 10. The system of claim 9, furthercomprising: a mixture sensor coupled to the output of the mixer and athird input to the controller.
 11. The system of claim 10, wherein themixture sensor is a pH sensor.
 12. The system of claim 9, wherein thecontroller includes: a first output coupled to a control input of thefirst control valve; a second output coupled to a control input of thesecond control valve; a first input coupled to an output of the firstflow sensor; a second input to an output of the second flow sensor; anda control scheme.
 13. The system of claim 9, wherein the control schemeincludes a proportional, integral, derivative (PID) control.
 14. Thesystem of claim 9, wherein the mixer includes: a first control valvecoupled between an output of the first flow sensor and a mixturemanifold; a second control valve coupled between an output of the secondflow sensor and the mixture manifold; and a mixer output control valvecoupled between the mixture manifold and a mixture distributor.
 15. Thesystem of claim 9, wherein the first pump includes a pressure regulator.16. The system of claim 9, wherein the pump includes a tubephram-typepump.
 17. The system of claim 9, wherein the pump includes a rotary-typepump.
 18. The system of claim 9, wherein the pump has a dischargecapacity of between 15 and 250 ml per minute.
 19. The system of claim 9,wherein the pump produces fewer chained particles.
 20. A mixing systemcomprising: a first pump having an input coupled to a first chemicalsupply; a first flow sensor coupled to an output of the first pump; asecond pump having an input coupled to a second chemical supply; asecond flow sensor coupled to an output of the second pump; a mixerhaving inputs coupled to the output of the first flow sensor and theoutput of the second flow sensor; and a controller configured to receivesignals from the first and second flow sensors and to produce controlsignals for the first and second pumps and the mixer and configured tocause a mixture of the first and second chemicals upon a demand from aCMP process.